Steam-boiler ftjbnace



Feb. 3, 1931. J. c. HOBBS STEAM BOILER FURNACE Original Filed July 23, 1925 INVENTOR BY W 5%ATTORNEY5 Patented Feb. 3, 1931 UNITED STATES PATENT, OFFICE TAKES G. HOBBS, OF PAINESVILLE, OHIO STEAM-BOILER FURNACE Continuation of application Serial No. 45,453, filed. m as, 1925, and in Great Britain This application filed October 19, 1929. Serial No. 400,773.

My present invention relates to steam boiler furnaces, and particularly to improvements in the slag screens used in such furnacesin connection with the burning of powdered fuel.

My present application is a continuation of my application Serial No. 45,453, which was filed in the United States Patent Oflice on or about July 23, 1925.

My invention will be best understood from the following description and the annexed drawing which shows a vertical section of a typical boiler and its furnace embodying one form of my invention. 7 v

In the illustrative arrangement, the furnace chamber is of the usual rectangular cross-section with a front wall 10 and a rear wall 11, the furnace having a short roof 12 through which projects one or more powdered fuel burners 13 to direct the fuel downward along the front wall 10 where the fuel is ignited and upward into and amongst the V boiler tubes 14 to the gas outlet 15. all in the usual manner. The boiler has uptake headers 16 and downtake headers 17. each connected to the steam and water drum 18.

Extending across the front of the furnace at its lower part is a cross header 19 to which is connected a row of slag screen tubes 20 extending across the lower part of the furnace chamber. The tubes 20 are inclined to the horizontal and. in addition, thepart of each tube near the rear wall is bent upward on a curve whose center of curvature is above the tube so as to tend to merge more or less into a rear wall cooling tube 21. one of the tubes'21 being provided for each of the tubes 20. A tube 20 is connected toa tube 21 by a curved fitting 22 provided with a handhole having a closure 23 of the usual type. The tubes 21 extend along the'face of the rear wall 11 in the illustrative embodiment, and then are bent outward to enter a header 24 which is connected bv a pipe 25 and nipples 26 to the drum 18. Similarly the header 19 is connected through a pipe or pipes 27 and nipples 28 to the drum 18. By removing the closure 23 for the curved fitting 22, a tube cleaner may be inserted through the opening to clean January 20, 1928.

either the slag screen tube or the riser tube connected by said fitting.

It' ill be noted that the rear wall 11' is made up in sections with special tile extending through the wall and that the fitting 22 is located in a space beneath a special tile 29 supported on metal members 30 and 31so as to form a recess in the lower portion 11 of the rear wall 11 by which the fitting, while outside of the furnace chamber, will nevertheless be accessible from the exterior and, at the same time, will provide a curved connection between each tube 20 and atube 21. The efli'ect of bending the tube 21, aided by the curvature of the fitting 22, provides a smooth continuous path for the flow ofwater from the header 19 through the tubes 20 and up into the boiler.

tubes are subjected to intense heat.

Moreover, by bending the tubes 20 upward,

the greater portion of the tubes,'particularly that part directly beneath. the powdered fuel burners, can remain substantially straight, while, at the same time, the upward bend carries the connection between the tubes 20 and the tubes 21 (that is, in the illustrative embodiment, the fitting 22) to a higher point than would be otherwise possible, so thatthe sloping rear wall 32 of the ash-pit may be started at a higher point on the rear wall; Another advantage of curving the slag screen tubes is that less bending strains are set up in the tubes, since the weight of the tube and the water which fills it is carried, partly at least, by tension in the tube. If, for instance, the tube were bent into a true catenary, there would be no transverse strains in the tube. Bending in the manner shown produces some of the effect of a catenary. This carrying of the load partly in tension is particularly of advantage where it is desirable to use small tubes, because of high boiler pressures, or where the distance between the front and rear furnace walls is great, so that the tubes are long between their end supports. In either case, if the tube were straight, its weight and that of the Water therein would be so great proportionally to the strength ofthe tube to resist transverse bending, so that the tube might sag to such an extent as to make it impractical. By

curving the tube, and thus transferring the pull or gravity on the tube partly into tension, small diameter tubes with wide spacing between the end supports can be used witherating tubes 20 as slag screen tubes uhich are located in the lower part of the furnace chamber, it will be understood that they may be located in any desired portion of the chamber.

I. claim:

1. A furnace chamber having a powdered fuel burner, slag screen tubes extending across the lower part of the chamber, water i'nlet'connections to said tubes at one end and water and steam outlet connections tothe other end whereby water is circulated therethrough, the end of each tube adjacent said outlet end having a long bend therein with its center of curvature above the tube and the remainder of the tube being substantially straight.

2. A furnace-chamber having a powdered fuel burner, slag screen tubes extending across the lower part of the chamber, with one end of each tube higher than the other end, water inlet connections to the low ends ofsaid tubes and steam and water outlet connections to the high ends of the tubes whereby water is circulated therethrough,

the end of each tube adjacent the high end having a long bend therein with its center of curvature above the tube and the remainder of the tube being substantially straight.

3. A furnace chamber having a powdered fuel burner, slag screen tubes extending across the lower part of the chamber, vertically disposed wall cooling tubes extending along a furnace wall, each having its lower end connected to one end of one of said slag screen tubes, connections to said cooling tubes and said slag screen tubes whereby water is circulated therethrough, the end of through the walls thereof with the rear end i of each tube higher than the front end, vertically disposed wall cooling tubes extending along the rear furnace wall, each having its lower end connected to. the rear end of one of 'said slag screen tubes, connections to said cooling tubes and said sla screen tubes whereby water is circulate therethrough, the end of each slag screen tube adjacent the rear furnace wall having a lon bend therein with its center of curvature a ove the tube and the remainder of the tube being substantially straight.

5. A furnace chamber having a powdered fuel burner, slag screen tubes extending across the lower part of the chamber, vertically disposed wall cooling tubes extending along the rear furnace wall, each having its lower end connected to an end of one of said slag screen tubes, connections to said cooling tubes and said slag screen tubes. whereby water is circulated therethrough, the end of each slag screen tube adjacent the end connected to a cooling tube having a long bend therein with its center of curvature above the tube and the remainder of the tube being substantially straight, the connection between each slag screen tube and a wall cooling tube comprising a curved fitting forming a curved path for the water flowing from the slag screen'tube into the wall cooling tube.

6. A furnace chamber having a powdered fuel burner, slag screen tubes extending across the lower part of the chamber, water inlet connections to said tubes at one end and water and steam outlet connections to the other end whereby water is circulated therethrough, the end of each tube adjacent said outlet end being formed with a curve approximating a catenary curve with its concavity upwards.

7. In combination, a furnace chamber, slag screen tubes extending across the lower part of thefurnace chamber, the end of each slag screen tube adjacent its outlet end having a long bend therein with the center of curvature above the tube, upwardly extending riser tubes and fittings connecting the ends of the respective slag screen tubes and said riser tubes, each of said fittings being provided with means whereby both of said tubes may be cleaned through said fitting, and water inlet connections leading to the opposite ends of said slag screen tubes.

8. In combination, a furnace chamber, slgg screen tubes extending across the lower part of the furnace chamber, the end of each slag tubes extending across said cham screen tube adjacent its outlet end having a long bend therein with the center of curvature above the tube, upwardly extending riser tubes and fittings connecting the ends of the respective slag screen tubes and said riser tubes, each of said fittings being provided with a handhole and a closure therefor whereby both of said tubes may be cleaned through said fitting, and water inlet connections leading to the opposite ends of said slag screen tubes.

9. In combination, a furnace chamber having a powdered fuel burner, steam generating er, water inlet connections to said tubes at one end and water and steam outlet connections to' the other end whereby water is circulated therethrough, the end of each tube adjacent said outlet end being formed with a curve approximating a catenary curve with its concavity upwards.

10. In combination, a furnace chamber, means for burning fuel therein, steam generatin'g tubes positioned to be heated through the combustion of said fuel, water inlet connections to said tubes at one end and water and steam outlet connections to the other end whereby water is circulated therethrough,

the end of each tube adjacent said outlet end being formed with a curve approximating a catenary curve with its concavity upwards.

11. A furnace chamber having a powdered fuel burner, slag screen tubes extending across said chamber, said powdered fuel burner discharging into the combustion chamber above said slag screen tubes, water inlet connections to said tubes at one end and water and steam outlet connections to the other end whereby water is circulatedtherethrough, the end of each tube adjacent said outlet end being formed with a curve approximating a catenary curve with its concavity upwards.

JAMES C. HOBBS. 

